Lesson 3-1 SURFACE-PREPARATION EQUIPMENT
Before you apply any protective-coating material, it is important to prepare the work surface. If the surface is scaly, dirty, oily, or dusty, the coating will not adhere satisfactorily.
3-1. Hand-Operated Tools
There are numerous hand-operated tools; however, only the tools you are most likely to use in your work will be discussed in this lesson.
a. Wire Brushes. Hand wire brushes (Figure 3-1) are used to remove loose paint from wood, masonry, or metal surfaces that are situated in close places and where power equipment cannot be operated economically. The brushes are made of different sizes and shapes depending on the stiffness required. Brush bristles are small- or large-gauged wires made of steel, brass, or stainless steel. Use steel wire bristles on steel, wood, and masonry; brass wire bristles on brass; and stainless-steel wire bristles on stainless steel. To prevent damage, store wire brushes by hanging them on a wall.
Figure 3-1. Hand wire brushes
b. Painter's Dusters. Painter's dusters are used to remove fine dust before painting. Dusters are usually flat or oval in shape and are fitted with handles similar to those on paintbrushes. Store painter's dusters by hanging them on a wall or by wrapping paper around them and laying them flat. Never stand dusters on their bristles.
c. Scrapers. Paint scrapers are grouped as pull, push, or molding (Figure 3-2). Scrapers will vary based on their intended uses; for example, one scraper type is used to remove deteriorated paint from the surface, and another is used to remove plane and mill marks from wood surfaces (Figure 3-3). Scrapers made of flexible steel must be kept sharp to do good work. Figure 3-4, demonstrates how hand-scraper edges are sharpened. The cutting edges of a cabinet scraper (Figure 3-5) and a scraper plane (Figure 3-6) are sharpened similarly to the hand scraper. You should never toss scrapers into a toolbox with other tools as this will nick the sharp edges and make it necessary to resharpen them.
Figure 3-2. Pull, push, and molding scrapers
Figure 3-3. Wood scraper
Figure 3-4. Sharpening hand-scraper edges
Figure 3-5. Cabinet scraper
Figure 3-6. Scraper plane
d. Putty Knives. Among the many different putty knife styles available (Figure 3-7), there are those with short, stiff blades; long, flexible blades; wide blades, and narrow blades. The original purpose of putty knives was to gaze window panes into window frames, but they are often used to scrape old paint surfaces and apply joint cement to sheetrock walls. Putty knives seldom need sharpening, but they should be stored in a manner to prevent damage to the blades.
Figure 3-7. Putty knife
e. . Cold Chisels. Cold chisels (Figure 3-8) are used to chip paint or scale from metal surfaces, and the chisels are available in different widths and lengths. Chisels are sharpened by grinding their heads on a grinding wheel to restore the bevel, which is usually at a 60- to 70-degree angle. Occasionally, you may need to remove the burrs from the heads if the heads have mushroomed.
Figure 3-8. Cold chisel (3/4 inch)
f. Files. Files are steel tools used for cutting and smoothing metal and wood. A wood rasp is a course file that differs from the ordinary file in teeth shape and size. There are over 3,000 types and kinds of files and rasps. The most common types are shown in Figure 3-9. Clean files with a file card, which is a wood handle with a brush on one side and fine-wire teeth on the other. Preserve the sharpness of files and rasps by storing them in a rack. If you need to carry files in a toolbox, wrap them individually in cloth or paper to protect their teeth. To prevent rusting, keep files dry and do not use rust-preventive compound on them. Files are very brittle, so do not hammer files or use them as pry bars.
Figure 3-9. Files
g. Abrasives. There are many different abrasive types, and each type varies in grit, size, and use. Among the abrasive types available are—
- Flint is frequently used because of its low cost, but it dulls and wears quickly.
- Garnet is a natural mineral, and it is the choice abrasive for hand-sanding and wood-finishing.
- Emery is a natural mineral that comes from Turkey or Greece. It is a good cutting agent, but it abrades slowly. Emery is primarily used for metal-polishing and rust-removing.
- Aluminum oxide is backed with production paper, and it is used on wood and light-weight metal surfaces because aluminum oxide's tough coating cuts faster and longer than flints.
- Silicon carbide is produced by fusing silica and coke and it is a sharp abrasive. It is used on lacquers, plastics, composition materials, or metals for wet and dry sanding.
(1) Abrasives are fastened to paper, cloth, or fiber and are available in sheets, belts, or discs for use on sanders. The following are the weights and uses for paper- and cloth-backed abrasives:
(a) Paper-backed abrasive comes in four popular weights that are designated as A, C, D, and E:
- A is soft and flexible and is used where flexibility is desired.
- C and D are thicker and are used where flexibility is not necessary.
- E is heavier and is used mostly for machine sanding.
(b) Cloth-backed abrasive comes in two weights, J and X:
- J is used with emery for hand sanding.
- X is used mostly with power tools.
(2) In the past, manufacturers listed their abrasives by a complicated number system. A newer system labels the paper grades by terms such as fine, medium, and coarse. You will find both systems in use today. In the left column, of Table 3-1, is a list of the new label grades. The relating old number grades are found in the middle and right columns for garnet, aluminum-oxide, and flint. Use Table 3-2, to select the correct abrasive type and size when selecting abrasives based on a work surface or an intended use.
Table 3-1. Label and number grade comparisons
Table 3-2. Selecting abrasives by work surface or intended use
(3) There are three powdered abrasives: pumice stone, rottenstone, and jeweler's rouge. Powdered abrasives are used primarily on furniture for fine-woodwork finishing, to smooth the finishes between coats of paint, and to polish metal surfaces. Pumice stone comes in grades F, FF, FFF, and FFFF. The best all-around powdered abrasive to use is FFF. Only one grade is available for rottenstone or jeweler's rouge.
h. Metallic Wools. Metallic wools have a variety of uses, and in many areas, they are better than abrasives. There are four major types of metallic wools: aluminum wool for use on aluminum; copper wool for use on copper; stainless-steel wool for use on stainless steel; and steel wool (the most common type) for use on steel, iron, and wood. Metallic wools come in six grades that number from 3 (coarsest) to 3/0 (finest). Use Table 3-3 as a guide for selecting the correct steel-wool grade.
Table 3-3. Selecting steel-wool grades
i. Blowtorches. Use blowtorches (Figure 3-10) to remove paint from interior and exterior surfaces. Blowtorches are available in many forms and use gasoline, alcohol, acetylene, or petroleum gas for fuel.
Figure 3-10. Blowtorch
(1) To fill a blowtorch, turn it upside down and unscrew the filler plug. Pour unleaded gasoline (leaded gasoline will clog the torch) into the base, which serves as a funnel. When the tank becomes full, replace the filler plug and wipe off the excess gasoline. Turn the blowtorch upright, then operate the air pump to put pressure on the gasoline in the reservoir. Pour a small amount of gasoline in the bowl located below the vaporizing assembly, and ignite the gas. You can also place gasoline in the bowl by opening the needle valve by a small amount and allowing the gasoline to drip into it. When the gasoline in the bowl is almost burned, open the needle valve and the torch will light. In addition to conventional blowtorches, there are torches that use pressurized petroleum. These torches are very convenient, especially for removing paint from small areas.
(2) A blowtorch can be dangerous if it is not used correctly. The following safety rules apply to the use of a blowtorch:
- Never light a blowtorch in an unventilated room.
- Always set a blowtorch on a solid surface while lighting it.
- Never move a blowtorch while gasoline is burning in the bowl located below the vaporizing unit.
- Never light a blowtorch in the presence of wind.
- Never use a blowtorch near draperies or curtains.
- Never use a blowtorch near windows as its heat will crack the glass.
- Always go back over your work to ensure that no fire exists.
j. Heat Guns and Plates. Heat guns (Figure 3-11) work best on even surfaces, such as trim and molding. Heat plates make fast work of flat surfaces, such as siding. While these tools generate enough heat to set wood or hidden debris afire, the risk posed is much less than using blowtorches.
Figure 3-11. Heat gun
k. Caulking Guns. Caulking guns come in two different styles. One style is cartridge-loaded, and the other is loaded by unscrewing the gun end and filling the body with bulk compound. The guns are used to—
3-2. Power-Operated Tools
You can save much time and effort by using power-operated tools. Additionally, several operations can be performed by the same power unit by using different attachments. For example, one power unit can accommodate a grinder, a sander, or a buffer.
a. Power Wire Brushes. Use power wire brushes to conserve man-hours in large work areas. Use the brushes to remove paint from wood, masonry, or metal surfaces, and corrosion from metal surfaces. You should use brushes made of fine spring steel. Figure 3-12, shows two wire-brush types that are used on an electric or air motor, a flexible-shaft machine, or in the chuck of an electric drill. They can also be mounted on a stationary or portable grinder. No maintenance is necessary; however, replace brushes when they wear down.
Figure 3-12. Power wire brushes
b. Power Sanders. Use power sanders to remove paint or corrosion from metal and wood surfaces and to smooth surfaces for finishing. There are many types of power sanders available, but the sanders you will use most are the portable vibrator; the belt, disc, and drum floor sander; and the floor edger. You must wear safety goggles or a face mask while using sanding machines. Start all portable sanders before placing them on the work area.
(1) Portable vibrator sander. A portable vibrator sander (electric) is a small machine with an abrasive sheet clamped on it. An orbital vibrator sander, shown in Figure 3-13, is small enough for you to hold in one hand while sanding. This tool is excellent for removing old paint and varnish and for sanding drywall joints. No maintenance is necessary on this machine.
Figure 3-13. Orbital vibrator sander
(2) Portable belt sander. Use a portable belt sander (Figure 3-14) for finishing work and for fast and efficient sanding of wood surfaces. The sander uses an endless, abrasive-coated belt that runs over two flat pulleys. You will need to use both of your hands to operate the sander, and you must use extreme caution to ensure that the sander does not cut the wood surface too deeply. Occasionally clean the sander with compressed air.
Figure 3-14. Portable belt sander (with dust bag)
(3) Portable disc sander. Use a portable disc sander (Figure 3-15) on metal surfaces or to remove badly flaked paint on wood surfaces. One type fits the chuck of an electric drill or a power tool. The sander's abrasive discs come in various grits for various tasks and are easily replaced.
Figure 3-15. Portable disc sanders
(4) Drum floor sander. The drum floor sander (Figure 3-16) uses an abrasive belt that is similar to the belt sander. It is used to sand new or painted wood floors; however, because of its size, the drum floor sander cannot sand close to walls and in corners. The only maintenance required on this machine is to occasionally blow compressed air through the motor and replace the belt when it becomes worn.
(5) Floor edger. The floor edger (Figure 3-17) is very similar to the portable disc sander; in fact, their abrasive discs are interchangeable. The floor edger is designed to sand close to walls and in corners, thus eliminating much hand sanding. Clean the edger by blowing compressed air through the motor occasionally.
Figure 3-16. Drum floor sander
Figure 3-17. Floor edger
c. Power Buffers. There are two types of power buffers; one type is used to buff wood floors, and the other type is used to put a high polish on metal surfaces. Buffers are cleaned in the same manner as other power equipment by removing dust from the motor with compressed air.
(1) Floor buffer. A floor buffer weighs approximately 30 to 40 pounds. The polishing pads vary in size from 12 to 22 inches and are made of nylon, animal hair, or hog bristles. The pads can be obtained in coarse-, medium-, and fine-bristled materials.
(2) Metal buffer. A metal buffer is a rag wheel that is installed on a power tool or a bench grinder. It is also used with a flexible-shaft machine or in a portable drill that is equipped with a special chuck. The rag wheel is charged with a buffing compound (jeweler's rouge, rottenstone, or pumice). It is essential that you wear a face mask and gloves to protect you from fine particles that come from the rapidly turning, charged rag wheel. The fine particles are capable of cutting your flesh.
d. Portable Power Grinders. Use grinders to remove scale or encrustation from metal surfaces. The tool, as shown in Figure 3-18, is driven by an electric motor that uses 110-volt, 60-cycle alternating current. The electric motor in the grinder is geared and has a chuck. The features make it possible to attach different grit-sized abrasive wheels. The action of the grinder may be clockwise or counterclockwise. You must wear goggles when you are using a grinder, and your safety guard must be in place. You should use reinforced abrasive wheels and never exceed the operating speed indicated on the wheel blotter.
Figure 3-18. Portable power grinder
e. Descalers. Descalers are electric or pneumatic hammers with multiple-needle heads. The needles are interchangeable with a chisel-like unit. This tool is good for cleaning hard-to-get-at areas on metal surfaces, such as grooves, corners, crevices, rivets, protruding nuts or bolts, and gratings. The descaler operates with a reciprocating action and hammers the surface clean with wear-resistant alloy needles. This tool weighs approximately 4 1/2 pounds and is 14 to 20 inches long. When using this tool, you should wear goggles and a face shield or a hood.
f. Portable Abrasive Blasters.
(1) Use portable abrasive blasters (Figure 3-19) to remove paint from metal or masonry surfaces and corrosion from metal surfaces. Blasting is a very effective method of removing traffic markings from concrete paving.
Figure 3-19. Portable abrasive blaster
(2) Abrasive-blasting equipment is simple to operate. In fact, only 8 to 16 hours of operating time is required to acquire a basic knowledge of abrasive-blasting techniques. However, simple though the operation may be, each equipment type has its own peculiarities. Because of this, you should closely follow the operating instructions of the specific equipment to prevent damage to the equipment or to the material being cleaned.
(3) The abrasive blaster is operated by compressed air. The air pressure bombards the surface with the abrasive (sand, grit, split shot, or glass beads) at a high velocity. If the compressed air is furnished by a portable compressor, you must follow the manual for operating this particular compressor type.
(4) The following instructions are for a typical abrasive-blasting unit. You must check your operator's manual on your specific blaster, as each unit has its own peculiarities. You should—
Perform operator maintenance on the blaster as follows:
Discharge the leftover abrasive through the gun if the abrasive-blasting unit will not be in use for sometime. To remove the small quantity that is below the level of the pump inlet, open the drain valve at the bottom of the hopper.
g. Portable Vacuum Blasters. Use portable vacuum blasters for the same purposes as abrasive blasters. One big advantage of the vacuum blaster is that the used abrasive, debris, and dust are removed by the vacuum during the blasting process.
h. Steam Cleaners. A steam cleaner (Figure 3-20) consists of a metal cabinet that houses such components as an electric motor or gasoline engine and units for individual water, soap, and heating systems. A steam cleaner blends the detergent with water and pumps the solution into a heating unit, where it is partially vaporized. The heat, plus vaporization, generates pressure in the system. The solution is then directed to the cleaning hose and gun from which it is sprayed upon the surface to be cleaned. The detergent and spray, together with impact (friction) caused by high velocity, loosen and remove the dirt and encrustations. After you have completed the cleaning operation, the vaporized spray can be converted into a solid, high-velocity stream of water for rinsing the material you are cleaning.
Figure 3-20. Steam cleaner
i. Vacuum Cleaners. Before applying protective coatings, use industrial or domestic vacuum cleaning equipment to remove items such as dirt; dust; small, loose objects; and paper from surfaces and areas. To loosen the soil caked on the vacuum cleaner's inlet, use a soft-bristled brush.
Always remember to check the applicable TO or operator's manual when you are using any of the equipment or items discussed above or when performing maintenance.